Touch key design for one-handed thumb interaction with a mobile phone: Effects of touch key size and touch key location

Abstract

This study investigated effects of touch key sizes and locations on one-handed thumb input on a mobile phone. Three different touch key sizes (i.e. square shape with 4 mm, 7 mm, and 10 mm wide) and twenty-five locations were examined in an experiment. A total of thirty subjects participated in the experiment in which they preformed a task of pressing a single target on a small touch screen. Two time-related measures (first transition time and task completion time), number of errors, and subjective satisfaction (pressing convenience) were collected in the experiment. The results revealed that the touch key size of 7 mm and 10 mm provided the best performance for time-related measures, while the touch key size of 10 mm only provided the best results for the other measures. In addition, the usability of touch key locations was statistically analyzed. Touch key locations providing good usability (‘good regions’) were also identified for each measure. Recommendations were proposed for designing a touch user interface on a mobile phone based on the results of this study. Relevance to industry The touch user interface is in the limelight of the handset industry. This study conducted basic research to investigate the effects of touch key sizes and touch key locations for one-handed interaction. The results of this study could be used for designing a touch user interface to enhance the usability of mobile phones and other small devices with a touch screen as well.